Field of the Invention
This invention relates to systems and methods for storing data in tiered storage systems.
Background of the Invention
In the z/OS operating system, PDSE (partitioned data set extended) data sets are used to simply and efficiently organize related groups of sequential files, also referred to as “members.” Current versions of PDSE data sets may support multiple levels, or generations, of members. Using this feature, when a member is changed, a new member may be created and the older version of the member may be retained, up to a specified number of generations. This feature advantageously enables members to be recovered in cases of accidental deletion, user errors, data corruption, or the like. This feature also allows multiple generations of a member to be retained for archival reasons. The retained generations may be structured in a first in, first out (FIFO) configuration, such that an oldest generation is discarded when the retained generation limit is reached.
Unfortunately each generation in a PDSE data set is retained in its entirety, resulting in the multiplication of space requirements for the PDSE dataset. Additionally, member generations are typically only utilized in the event they need to be recovered, meaning that most of the space allocated to a PDSE data set will never be accessed. Such inefficient use of space may be particularly costly when storing performance-critical PDSE datasets on expensive storage media such as solid state drives (SSDs). For example, a PDSE data set containing a critical load library may be stored on SSD for performance reasons. Such a PDSE data set may be configured to retain one hundred generations of each member. This requires allocating approximately one hundred times the space required to store the primary members. The vast majority of this allocated space will contain member generations that are never accessed but nevertheless consume valuable SSD space.
In view of the foregoing, what are needed are systems and methods to more efficiently use space when using PDSE data sets. Ideally, such systems and method will enable PDSE member generations to be stored on multiple storage tiers to reduce use of expensive storage media.